A. Psychophysics: (1) Theoretical studies. The theoretical studies of analysis of flicker responses in terms of luminance mechanisms will be extended for both temporal and spatial modulation sensitivity. The characteristics of parallel mechanisms revealed in this way will be explored. (2) Fundamental studies. The nature of the high temporal frequency asymptote will be studied, and the role of lateral inhibition in low frequency portion of the function will be explored by the direct method orginally proposed. (3) Clinical studies. Peripheral flicker sensitivity functions will be measured for a range of retinal diseases including glaucoma, retinitis pigmentosa, juvenile diabetic retinopathy, and optic neuritis. Fundamental studies have indicated that there are at least 4 types of change in the function that can occur independently: (a) change in the high frequency asymptote; (b) shift across all temporal frequencies; (c) overall sensitivity loss; and (d) sensitivity loss selective to temporal frequency (high, medium or low). The diseases will be categorized in terms of these losses, taking into account the degree of severity of the disease. B. Electrophysiology: (1) Fundamental studies. The fundamental studies will proceed with the quantification of the details of spatiotemporal frequency specificity of the VEP as a function of ocularity, retinal location, and variables of stimulus configuration. Our current findings show reliable tuning in the responses to the extent of plus or minus 0.5 octave of spatial frequency and plus or minus 0.1 octave of temporal frequency (minus 3db), so great detail is required. We shall determine the maximum temporal frequency limits for luminance, contrast and edge specific responses, to establish the optimum frequency for stimulation in clinical diagnosis. (2) Clinical studies. The main clinical studies will be in strabismic and other types of amblyopia, to determine the spatial frequency and orientation specificity of pathological response, both monocularly and for binocular interactions. We shall also develop the pattern VEP as a measure of acuity in infants and other non-verbal observers.